Butt Welding and Electrofusion

Butt Welding

Butt Welding is the name given to hot plate welding of thermoplastic pipes. This involves the simultaneous heating of both ends of the pipeline that is to be joined until a molten state is achieved on each contact surface in the bead up process. These molten ends are then forced together under constant pressure until the joint has formed with strength comparable to, or greater than, the pipe itself.

Electrofusion

Electrofusion is the name given to resistive implant welding of thermoplastic pipes. The process uses heat generated from electricity to melt both the pipe wall and the pipe fitting, thus joining all components and creating a completely homogenous joint that is as strong as the pipe itself.

Influencing factors for using Butt Welding or Electrofusion for joining PE pipes:

• Accessibility – Electrofusion is particularly suited to installations where access is difficult, such as in trenches or around other pipes, or where pipes are fixed in situ and require slip couplers to make a flush fitting joint.
• Pipe size – electrofusion is applicable to pipe sizes from 16mm to 710mm, whereas butt fusion is applicable to pipe sizes from 50mm to 2000mm.
• Pipe material – Thanks to its versatility, electrofusion can be used to weld together pipes or fittings from different PE (eg: MDPE to HDPE ) materials and different thicknesses as long as there is compatibility of melt flow index and raw material density.
• Pipe structure – In butt fusion welding, pipes to be joined must have the same wall thickness, whereas with electrofusion a difference in wall thickness can be accommodated. Electrofusion can also be used to join certain types of multiple layer pipes, e.g. nylon lined polyethylene pipe for the conveyance of fuel.
• Installation method – If the pipe is to be installed using a ‘no-dig’ technique such as directional drilling, or the pipe is to be used as a close fit lining in an existing pipeline, then electrofusion is not favoured, due to the outer dimensions of the joint fittings.